Hand-warmer Design Lab
Background: The ideal hand warmer increases in temperature by 20oC (but not much more) as quickly as possible, has a total volume of about 50 mL, costs as little as possible to make, and uses chemicals that are as safe and environmentally friendly as possible. You will carry out an experiment to determine which substances, in which amounts, to use in order to make a hand warmer that meets these criteria.
Purpose: Design a solution for a hand-warmer that has a volume of 50mL go up approximately 20⁰ C, using about 10 grams of salt. A hand-warmer simply has a salt dissolve in water and release heat.
Part 1: Determination of cost efficiency for each salt
Create a procedure that allows you to do the following:
Determine the ΔHrx’n for each salt. ΔHrx’n = .
From ΔHrx’n, determine the cost efficiency (CE) of each salt. CE =
Materials:
Thermometer
Sodium chloride (NaCl)
Balance
calcium chloride (CaCl2)
100 mL graduated cylinder
sodium carbonate (Na2CO3)
Scoops
Styrofoam cups with lids (calorimeter)
Dixie cups or weighing boats
Sodium acetate (NaC2H3O2)
stirring rod
Lithium chloride (LiCl)
Magnesium sulfate (MgSO4)
Ammonium nitrate (NH4NO3)

Data:
You must create a data table indicating:
amounts of water and salt used in each trial
initial and final temperature of solution in each trial
Calculations:
You must calculate (show work including all relevant dimensional analysis) for:
Temperature change (ΔΤ)
q (the specific heat of your solution is 4.18 J/g⁰C – same as water)
ΔHrx’n
Cost efficiency (CE)

Cost: Use the chart below to help in calculating cost efficiency (Hint: convert to $/1g for the process)
Substance
Cost in $ per 500 g
NaCl
3.95
CaCl2
6.55
NaC2H3O2
12.90
Na2CO3
6.15
LiCl
32.75
NH4NO3
9.05
MgSO4
22.90
Part II: Safety research.
Go to www. sciencelab. com and search each salt that is still a viable solution based on your calculations in part 1. Click on “view MSDS” for that substance. Read the Material Safety Data Sheet (that’s what MSDS stands for) and make a data table listing each salt and its safety issues.
Access information from 1 additional reputable website for more information on environmental/health effects for any of the salts.
Create a data table that ranks the remaining viable salts from most dangerous to least dangerous with a brief explanation of the danger(s) or lack thereof.
Part III: Selection and rationale:
Once you have finished Part I and Part II, you must reach a clear conclusion, choosing ONE of the chemicals to use as a hand-warmer. Remember you are a business and must keep an eye on safety, profit, and usefulness. Your conclusion statements must include (in this order):
Your unwavering choice of chemical to use.
Why your chemical choice is reasonable in terms of:
Heat generation (Create a clear ranking of temperature changes.)
Cost efficiency
Safety
Why your choice is better than other reasonable chemicals (compare specifically to at least 2 others).
Which chemical(s) is (are) not a realistic choice at all.
Include an error analysis for the calculations involving ΔHrx’n